Time

Time is the biggest factor for me.  The time it takes to cut and file the many inserts or printed coupons.  I tried the non-clipping route, with just having a small pile of inserts, but I got tried of constantly flipping through just to see if I had a certain coupon.  Only to find either I didn't have the said coupon or that I needed more for other items, let the flipping begin all over again.
For me the coupon clipping and filing into my binder works best.  However, time doesn't.  I sometimes try to recruit my family to help. They do say they will help, but then I tell them it's okay.  If you can make it a family thing, it does save you on time.  An added bonus  is you get to spend family time together so couponing won't take away from that.  Also you are teaching your children about saving.  Teaching a child how to save at a young age could be beneficial to them as a teenager or even an adult.
Even if you only have five minutes a day to cut and file coupons do it.  See how much savings you can rake in with those five minutes.  Adjust it some until you get a routine down that works for you.